Preparation of recording materials for inkjet printers

ABSTRACT

A process for the preparation of recording materials for inkjet printers by applying aqueous coating compositions to one or both sides of a sheet of paper which has been treated with size, where the coating compositions contain from 20 to 200 g/l of starch and from 1 to 50 g/l of a copolymer which is obtainable by emulsion copolymerization of 100 parts by weight of a monomer mixture comprising 
     (a) from 10 to 65 parts by weight of styrene, α-methylstyrene, acrylonitrile and/or methacrylonitrile, 
     (b) from 30 to 85 parts by weight of acrylic and/or methacrylic esters of alcohols having 1 to 18 carbon atoms, 
     (c) from 5 to 25 parts by weight of monomers containing tertiary and/or quaternary amino groups, and 
     (d) from 0 to 20 parts by weight of other monoethylenically unsaturated monomers 
     in an aqueous medium in the presence of from 12 to 300% by weight, based on the monomers, of at least one natural or synthetic protective colloid.

The invention relates to a process for the preparation of recordingmaterials for inkjet printers by applying aqueous coating compositionsto one or both sides of a sheet of paper which has been treated withsize.

DE-A-30 16 766 discloses recording materials for inkjet printers, whichare prepared, for example, by coating a sized paper with atalc-containing aqueous solution of gelatin or with an aqueous solutionof hydroxyethylcellulose and polyethyleneimine, and then drying andcalendering the coated paper.

DE-A-31 32 248 discloses inker recording materials consisting of asupport coated with at least one basic latex polymer. According to theexamples, a sheet of sized paper is coated with an aqueous solution,containing aluminum silicate, of unspecified polymers and gelatin, andthen passed through a calender.

EP-A-0 387 893 relates to a recording sheet for inkjet printers. Therecording sheet consists of a base layer which on one side has anink-receiving layer and on the other side has a layer which preventspenetration of the ink.

The subject of EP-A-0 445 327 is a recording material suitable for theinkjet printing method that consists of a sized base paper with apolyolefin coating on one side and with, on the other side, anink-receiving layer which consists of a mixture of gelatin and ricestarch.

EP-B-0 257 412 and EP-B-0 276 770 disclose sizing agents for paper whichare based on finely divided, aqueous dispersions of copolymers which areobtainable by copolymerizing ethylenically unsaturated monomers byemulsion polymerization in the presence of degraded starches. Themonomer mixtures which are polymerized in the aqueous solution of adegraded starch comprise

(a) from 20 to 65% by weight of acrylonitrile and/or methacrylonitrile,

(b) from 80 to 35% by weight of an acrylic ester of a monohydricsaturated C₃ -C₈ alcohol and

(c) from 0 to 10% by weight of other ethylenically unsaturatedcopolymerizable monomers.

Monomers of group c) which can also be employed if desired are monomerscontaining tertiary and/or quaternary amino groups. The sizing agentscan be employed in both the engine sizing and the surface sizing ofpaper.

It is an object of the present invention to provide a process for thepreparation of inexpensive recording materials for inkjet printers. Therecording materials are to ensure a high ink density and good waterresistance of the inkjet-printed image.

We have found that this object is achieved, in accordance with theinvention, by a process for the preparation of recording materials forinkjet printers by applying aqueous coating compositions to one or bothsides of a sheet of paper which has been treated with size, using ascoating composition an aqueous dispersion containing from 20 to 200g/lof starch and from 0.5 to 50 g/l of a copolymer which is obtainable byemulsion copolymerization of 100 parts by weight of a monomer mixturecomprising

(a) from 10 to 65 parts by weight of styrene, α-methylstyrene,acrylonitrile and/or methacrylonitrile,

(b) from 30 to 85 parts by weight of acrylic and/or methacrylic estersof alcohols having 1 to 18 carbon atoms,

(c) from 5 to 25 parts by weight of monomers containing tertiary and/orquaternary amino groups, and

(d) from 0 to 20 parts by weight of other monoethylenically unsaturatedmonomers

in an aqueous medium in the presence of from 12 to 300% by weight, basedon the monomers, of at least one natural or synthetic protectivecolloid, and if synthetic cationic protective colloids are used it isalso possible to carry out the emulsion copolymerization in the absenceof monomers of group (c).

The paper which is coated according to the invention can be composed ofany known base materials for papermaking: use can be made, for example,of ground wood, thermomechanical pulp (TMP), chemothermomechanical pulp(CTMP), pressure-ground pulp (PGW) and sulfite and sulfate pulp, each ofwhich can be short- or long-fibered and bleached or unbleached.Cellulose can also be used as a raw material for the production of thepulp. Suitable supports for the recording materials include both filledand unfilled papers. The content of filler in the paper can be up to amaximum of 30% by weight, and is preferably in the range from 5 to 25%by weight filler. Examples of suitable fillers are clay, kaolin, chalk,talc, titanium dioxide, calcium sulfate, barium sulfate, alumina, satinwhite or mixtures of these fillers. The paper used as support for therecording materials for inkjet printers are preferably engine-sizedbeforehand, but can also be surface sized. The sized paper has, forexample, Cobb values of <40 g/m², preferably from 20 to 25 g/m². Theweight per unit area of the papers is not critical, and is for examplein the range from 50 to 120 g/m².

The paper can be sized with any conventional sizing agents, for examplewith resin size, fatty alkyl diketenes or polymer sizes which aredescribed, for example, in EP-B 0 257 412 or in EP-B-0 276 770. Thenovel process for the preparation of recording materials for inkjetprinters can be coupled directly with papermaking by first of allforming the sheet of paper on the papermaking machine and then treatingit directly on one or both sides with the coating mixture to be employedin accordance with the invention, and drying it.

The coating composition, which is applied to one or both sides of thesized paper, consists of an aqueous dispersion containing starch in theabovementioned copolymer. Suitable starches are natural, digested orchemically modified starches, for example wheat starch, rice starch,potato starch, oxidatively degraded starches, cationic starch,hydroxyethyl starch, hydroxypropyl starch, amphoteric starches andacetylated starch.

If the starch is insoluble, it is dissolved by heating in an aqueousmedium at temperatures above the gelatinization point of the starch. Thecoating compositions contain from 20 to 200 g/l, preferably from 60 to100 g/l, of at least one starch or a starch mixture.

The coating compositions additionally comprise a cationic copolymerwhich is obtainable by emulsion copolymerization of 100 parts by weightof a monomer mixture comprising

(a) from 10 to 65 parts by weight of styrene, α-methylstyrene,acrylonitrile and/or methacrylonitrile,

(b) from 30 to 85 parts by weight of acrylic and/or methacrylic estersof alcohols having 1 to 18 carbon atoms,

(c) from 5 to 25 parts by weight of monomers containing tertiary and/orquaternary amino groups, and

(d) other monoethylenically unsaturated monomers

in an aqueous medium in the presence of from 12 to 300% by weight, basedon the monomers, of at least one natural or synthetic protectivecolloid, and if synthetic cationic protective colloids are used it isalso possible to carry out the emulsion copolymerization in the absenceof monomers of group (c). Monomers of group (a) are styrene,α-methylstyrene, acrylonitrile and/or methacrylonitrile. It is preferredto employ styrene and acrylonitrile. 100 parts by weight of the monomermixture used for the polymerization contain from 10 to 65 parts byweight, preferably from 20 to 50 parts by weight, of at least onemonomer of group (a).

Suitable monomers of group (b) are all acrylic and/or methacrylic estersof alcohols having 1 to 18 carbon atoms, for example methyl acrylate,ethyl acrylate, isobutyl acrylate, n-propyl acrylate, methylmethacrylate, ethyl methacrylate, isobutyl methacrylate, n-butylmethacrylate, n-butyl acrylate, isobutyl acrylate, isobutylmethacrylate, tert-butyl acrylate, tert-butyl methacrylate, 2-ethylhexylacrylate, 2-ethylhexyl methacrylate, neopentyl esters of acrylic andmethacrylic acid, isooctyl acrylate, isooctyl methacrylate, palmitylacrylate, palmityl methacrylate, stearyl acrylate and stearylmethacrylate. Group (b) esters which are preferably employed are acrylicand methacrylic esters of alcohols having 4 to 6 carbon atoms,especially the acrylic and methacrylic esters of n-butanol, sec-butanoland tert-butanol. 100 parts by weight of the monomer mixture used forthe copolymerization contain from 30 to 85 parts by weight, preferablyfrom 20 to 80 parts by weight, of a monomer or a mixture of at least twomonomers of group (b).

Suitable group (c) monomers are all monomers containing tertiary and/orquaternary amino groups.

These are preferably monomers which comprise a basic nitrogen atom,either in the form of the free bases or in quaternized form, andmonomers which have an amido group which can, if appropriate, besubstituted. Examples of suitable monomers of this kind areN,N'-dialkylaminoalkyl (meth)acrylates, for example dimethylaminoethylacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl acrylate,diethylaminoethyl methacrylate, dimethylaminopropyl acrylate,dimethylaminopropyl methacrylate, diethylaminopropyl acrylate,diethylaminopropyl methacrylate, dimethylaminobutyl acrylate,dimethylaminobutyl methacrylate, dimethylaminoneopentyl acrylate,dimethylaminoneopentyl methacrylate. Further suitable basic monomers ofthis group are N,N'-dialkylaminoalkyl(meth)acrylamides, for exampleN,N'-di-C₁ -C₃ alkylamino-C₂ -C₆ -alkyl(meth)acrylamides, such asdimethylaminoethylacrylamide, dimethylaminoethylmethacrylamide,diethylaminoethylacrylamide, diethylaminoethylmethacrylamide,dipropylaminoethylacrylamide, dipropylaminoethylmethacrylamide,dimethylaminopropylacrylamide, dimethylaminopropylmethacrylamide,diethylaminopropylacrylamide, diethylaminopropylmethacrylamide,dimethylaminoneopentylacrylamide, dimethylaminoneopentylmethacrylamideand dialkylaminobutylacrylamide. Further suitable monomers of this groupare 4-vinylpyridine, 2-vinylpyridine and/or diallyl(di)alkylamines inwhich the alkyl group has 1 to 12 carbon atoms. In copolymerization, theabovementioned basic monomers are employed in the form of the freebases, as salts with organic or inorganic acids or in quaternized form.Carboxylic acids suitable for forming salts are, for example, thosehaving 1 to 7 carbon atoms, for example formic acid, acetic or propionicacid, benzenesulfonic acid, p-toluenesulfonic acids or inorganic acids,such as hydrohalic acids, for example hydrochloric acid or hydrobromicacid. The basic monomers mentioned above by way of example can also beemployed in quaternized form. Examples of compounds suitable forquaternization are alkyl halides having 1 to 18 carbon atoms in thealkyl group, for example methyl chloride, methyl bromide, methyl iodide,ethyl chloride, propyl chloride, hexyl chloride, dodecyl chloride,lauryl chloride and benzyl halides, especially benzyl chloride andbenzyl bromide. The quaternization of the nitrogen-containing basicmonomers can also be undertaken by reacting these compounds with dialkylsulfates, especially diethyl sulfate or dimethyl sulfate. Examples ofquaternized monomers from this group are trimethylammoniumethylmethacrylate chloride, dimethylethylammoniumethyl methacrylate ethylsulfate and dimethylethylammoniumethylmethacrylamide ethyl sulfate.Other suitable monomers are 1-vinylimidazolium compounds of the formula##STR1## in which R¹ =H, C₁ -C₁₈ -alkyl or benzyl and X.sup.⊖ is ananion and R=CH₃ or C₂ H₅ and n=1 to 3.

The anion can be a halide anion or else a radical of an inorganic ororganic acid. Examples of quaternized 1-vinylimidazoles of the formula Iare 3-methyl-l-vinylimidazolium chloride, 3-benzyl-l-vinylimidazoliumchloride, 3-n-dodecyl-1-vinylimidazolium bromide and3-n-octadecyl-1-vinylimidazolium chloride. Instead of the quaternizedvinylimidazolium compounds it is also possible to employ thenonquaternized compounds or salts thereof in the copolymerization.

Preferred group (c) monomers which are employed are vinylimidazole,methylvinylimidazole, dimethylaminoethyl acrylate,methacrylamidopropyldimethylamine and the corresponding quaternizedproducts. The monomers of group (c) can be employed in thecopolymerization either alone or in mixtures with one another. 100 partsby weight of the monomer mixture contain from 5 to 25 parts by weight,preferably from 6 to 20 parts by weight, of at least one monomer ofgroup (c).

Suitable monomers of group (d) are other monoethylenically unsaturatedmonomers, which are different from the monomers of groups (a) to (c).Group (d) monomers which are preferably used are acrylic acid,methacrylic acid, acrylamide and/or methacrylamide. The monomers ofgroup (d) are used in the emulsion copolymerization, if appropriate, inorder to modify the copolymers comprising the monomers (a) to (c). Thequantities of group (d) monomers make up from 0 to 20 parts by weight,preferably from 0 to 15 parts by weight, per 100 parts by weight of themonomer mixture employed in the copolymerization.

The monomers are copolymerized by emulsion copolymerization in anaqueous medium in the presence of polymerization initiators, whichdecompose into free radicals under the polymerization conditions, and inthe presence of from 12 to 300% by weight, based on the monomers, of atleast one natural or synthetic protective colloid. Suitable naturalprotective colloids are all water-soluble proteins, partially degradedproteins, water-soluble cellulose ethers, native starches, degradedstarches and/or chemically modified starches. Suitable water-solubleproteins are, for example, gelatin and casein. Partially degradedproteins which are soluble in water can be obtained from water-insolubleor water-soluble proteins and are, for example, degraded gelatin,degraded soya protein and degraded wheat protein.

Examples of water-soluble cellulose esters are hydroxy-ethylcelluloseand methylcellulose.

Other natural protective colloids are natural starches which areobtainable by heating in an aqueous medium at temperatures above thegelatinization point of the starches. Also suitable are degradedstarches which are obtainable by hydrolytic, oxidative or enzymaticdegradation, and chemically modified starches, such ashydroxyethylstarch or hydroxypropylstarch. The degraded and chemicallymodified starches usually have a viscosity η_(i) of from 0.04 to 0.5dl/g, preferably from 0.05 to 0.45 dl/g.

Examples of suitable synthetic protective colloids are polyvinylalcohol, polyvinylpyrrolidone and/or water-soluble cationic copolymerswhich contain tertiary and/or quaternary amino groups. Polyvinyl alcoholand polyvinylpyrrolidone can each have molecular weights in the rangeof, for example, from 10,000 to 50,000. Like the other protectivecolloids, they are soluble in water. Further suitable protectivecolloids are cationic copolymers which can be prepared by solutionpolymerization of monomer mixtures comprising

(1) from 40 to 80% by weight of styrene, acrylonitrile,methacrylonitrile and/or acrylic or methacrylic esters of C₄ -C₁₈alcohols,

(2) from 15 to 50% by weight of a monomer containing tertiary and/orquaternary amino groups, and

(3) from 5 to 25% by weight of acrylic acid, methacrylic acid,acrylamide and/or methacrylamide

in saturated C₁ -C₅ -carboxylic acids, in esters of these carboxylicacids with saturated C₁ -C₆ alcohols, in saturated C₁ -C₆ alcoholsand/or in saturated ketones. The solution polymerization is preferablycarried out in acetic acid. Examples of other customary solvents forsolution polymerization are formic acid, isopropanol, isobutanol,n-butanol, acetone, methyl ethyl ketone, diethyl ketone, cyclohexanone,ethyl acetate, propyl acetate, n-butyl acetate, sec-butyl acetate and/orethyl propionate. A process of this kind is disclosed, for example, inEP-B-0 051 144.

If the cationic copolymers described above are employed as protectivecolloids in the preparation of the copolymers which are present in thecoating compositions, then the copolymers can comprise only the monomersof groups (a) and (b) in copolymerized form. They can then, therefore,be prepared in the absence of monomers of group (c) by emulsioncopolymerization of monomer mixtures comprising (a) and (b).

Natural protective colloids which are preferably employed arehydroxyethylcellulose, hydroxyethylstarch and/or hydroxypropyl-starch.

Preferred synthetic cationic protective colloids are prepared bysolution polymerization in acetic acid of monomer mixtures comprising

(1) from 40 to 80% by weight of styrene, acrylonitrile and/or acrylic ormethacrylic esters of C₄ -C₈ alcohols,

(2) from 15 to 50% by weight of vinylimidazole, methylvinylimidazole,dimethylaminoethyl acrylate, diethylaminoethyl acrylate,dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate,dimethylaminopropyl acrylate, dimethylaminopropyl methacrylate,dimethylaminoethylacrylamide, dimethylaminoethylmethacrylamide,diethylaminoethylacrylamide and/or diethylaminoethylmethacrylamide orthe corresponding neutralized or quaternized monomers, and

(3) from 5 to 25% by weight of acrylic acid, methacrylic acid,acrylamide and/or methacrylamide.

In the emulsion copolymerization, the protective colloids are preferablyemployed in quantities of from 25 to 160% by weight, based on themonomers. By the process of emulsion copolymerization, aqueousdispersions are obtained which usually have solids contents of from 5 to50% by weight, preferably from 10 to 35% by weight. This solids contentconsists of finely divided copolymers which are each coated with a shellof protective colloid. The diameter of the dispersed particles isusually from 30 to 250 μm, preferably from 35 to 200 μm. The emulsioncopolymerization is carried out in the presence of customarypolymerization initiators which are employed in the customaryquantities. Examples of suitable initiators are hydrogen peroxide,ammonium and alkali metal peroxodisulfates, organic peroxides,hydroperoxides and azo compounds. The emulsion copolymerization can ifdesired be carried out in the presence of polymerization regulators, soas to regulate the molecular weight of the copolymers. Examples ofsuitable molecular weight regulators are alcohols such as isopropanoland sulfur-containing regulators, such as tert-butylmercaptan,mercaptoacetic acid, mercaptopropionic acid and dodecylmercaptan. Thepolymer dispersions which are obtainable in the case of emulsioncopolymerization are, in order to prepare the solutions which are to beused in accordance with the invention as coating compositions, generallydiluted with water, or are added to an aqueous solution containingdissolved starch. The coating compositions obtainable in this waycontain, in addition to starch, from 1 to 50 g/l, preferably from 2.5 to30 g/l, of a copolymer which is obtainable by emulsion copolymerization.

The coating compositions can if desired also contain finely dividedpigments. Examples of appropriate pigments are calcium carbonate, chalk,precipitated chalk, clay, titanium dioxide, barium sulfate and gypsum.The particle diameter of the pigments is usually below 20 μm, preferablyin the range from 0.2 to 3 μm. The coating mixture can if desiredcontain one or more different pigments. The quantity of pigments in thecoating composition is, for example, from 0 to 400 g/l.

As already mentioned above, the coating compositions are preferablyapplied during papermaking to one or both sides of the surface of thepaper using in-line application machines. The quantities of emulsioncopolymer are, for example, from 0.01 to 0.1 g/m² per side of the papersurface. In accordance with the process of the invention, papers areobtained which are outstandingly suited to printing with inkjetprinters. These papers give the printed image the required brillianceand density and have a high water resistance.

Unless indicated otherwise, the parts and percentages in the examplesare by weight. The inkjet printability properties were assessed on thebasis of ink density, strikethrough and showthrough on the reverse side(ink density of the reverse side) and the water fastness of theinkjet-printed image (ink density after storage in water). For thesetests, the paper was printed in black in a DeskJet PLUS commercialinkjet printer from Hewlett Packard. The ink density of the printedimage was determined on a solid ink area using a Gretag D 182 printdensitometer from Gretag, 8105 Regensdorf, Switzerland. Showthrough andstrikethrough were measured with the same instrument by way of the inkdensity of the reverse side of the print.

To determine the water fastness, part of the printed image was placed indrinking water at room temperature for 5 minutes. The paper was thendried and the ink density was determined, again using the Gretag D 182.

EXAMPLES CHARACTERIZATION OF THE AUXILIARIES EMPLOYED IN THE EXAMPLES:

    ______________________________________                                                               Degree of                                                                     substitution Solids                                                 ηi    mol/mol glucose                                                                            content                                   Protective colloid                                                                         dl/g      unit         %                                         ______________________________________                                        Hydroxypropylstarch                                                                        1.07      0.1          83                                        Hydroxyethylstarch                                                                         1.23      0.1          83                                        Cationic potato starch                                                                     1.5        0.047       83                                        ______________________________________                                                               Degree of                                                                     substitution Solids                                                 Molecular mol/mol glucose                                                                            content                                                weight    unit         %                                         ______________________________________                                        Hydroxyethylcellulose  2.5          98                                        Polyvinyl alcohol                                                                          26,000                 97                                        Degree of hydrolysis:                                                         88%                                                                           Polyethylene glycol                                                                          9000                 100                                       ______________________________________                                    

α-Amylase is a relatively heat-resistant amylase. Using 16.7 mg of 100%pure α-amylase it is possible, in from 7 to 20 minutes at 37° C. and ata pH of 4.7, to degrade a total of 5.26 g of the starch Amylum Solubilefrom Merck.

Preparation of the emulsion copolymers

Dispersion 1

338 parts of water are initially introduced into a reaction vessel whichis fitted with reflux condenser and stirrer, and are mixed with 0.06part of calcium acetate, 14.7 parts of a commercial cationic potatostarch, 12.05 parts of polyethylene glycol having a mean molecular massof 9000 and 0.005 part of α-amylase, and the mixture is heated to 85° C.with stirring. After reaching 85° C., 0.085 part of α-amylase is added.After 20 minutes, a mixture of 7.2 parts of acetic acid and 9.6 parts ofa 1% strength aqueous solution of iron sulfate (0.096 part) in water isadded. 2.8 parts of 30% strength hydrogen peroxide are added and thedecomposition of the hydrogen peroxide is awaited. Then 26.8 parts of a45% strength solution of a vinylimidazole quaternized with dimethylsulfate, 3.6 parts of acrylic acid and 0.6 part of a 30% strengthhydrogen peroxide solution, and a mixture of 42.2 parts of styrene and42.2 parts of n-butyl acrylate is metered over the course of 2 hoursand, separately, an aqueous solution of 52 parts of a 1.62% strengthaqueous hydrogen peroxide solution is metered over the course of 2 hoursinto the reaction mixture. 1 hour after the end of addition of hydrogenperoxide, the reaction mixture is stirred again at 85° C. and thencooled. An aqueous dispersion is obtained which has a solids content of18.1%. The dispersion has an LD value of 73.

Dispersion 2

292 parts of water, 0.07 part of calcium acetate, 15.1 parts of acationic potato starch, 12.5 parts of polyvinyl alcohol having amolecular mass of 26,000 and 0.005 part of α-amylase are initiallyintroduced into a reaction vessel fitted with stirrer and refluxcondenser, and the mixture is heated to 85° C. with stirring. As soon asthis temperature has been reached, 4.4 parts of a 1% strength aqueousα-amylase solution are added, the reaction mixture is heated at 85° C.for 20 minutes, and then 7.5 parts of glacial acetic acid and 5 parts ofa 1% strength aqueous solution of iron(II) sulfate are added in one go.Then 4.1 parts of a 30% strength aqueous hydrogen peroxide solution areadded and the reaction mixture is stirred. After 20 minutes, 27.8 partsof a 45% strength aqueous solution of vinylimidazole which isquaternized with dimethyl sulfate, 3.75 parts by weight of acrylic acidand 0.83 part of a 30% strength hydrogen peroxide solution are meteredin, and the metered addition of a mixture of 25 parts of styrene and58.8 parts of n-butyl acrylate is commenced immediately. This mixture ismetered in over the course of 2 hours, and, simultaneously therewithover the course of 2.25 hours, 53.5 parts of a 2.1% strength aqueoushydrogen peroxide solution are added. Following the end of the additionof hydrogen peroxide, the reaction mixture is postpolymerized for 1 hourat 85° C. and then cooled. A dispersion is obtained which has a solidscontent of 22.9%. The dispersion has an LD value of 89.

Dispersion 3

415 parts of water, 0.12 part of calcium acetate, 17.2 parts of acationic potato starch and 14.9 parts of hydroxyethylcellulose togetherwith 0.6 part of 1% strength aqueous α-amylase solution are initiallyintroduced under nitrogen into a polymerization vessel which is fittedwith a reflux condenser and a stirrer, and the mixture is heated withstirring to 85° C. As soon as this temperature has been reached, 0.6part by weight of 1% strength aqueous α-amylase solution (0.004%) isadded. 20 minutes later, a mixture of 8.6 parts of glacial acetic acidand 5.7 parts of a 1% strength aqueous iron(II) sulfate solution isadded. 3.3 parts of 30% strength hydrogen peroxide are added and itsdecomposition is awaited. Then 0.71 part of 30% strength hydrogenperoxide is added and the metered addition of a mixture of 28.6 parts ofstyrene, 50 parts of n-butyl acrylate, 7.14 parts of methacrylic acidand 28.3 parts of a 50% strength aqueous solution of dimethylaminoethylacrylate quaternized with dimethyl sulfate is commenced immediately.Simultaneously with the monomer addition, which takes place over thecourse of 2 hours, the addition is begun of 61 parts of a 1.6% strengthsolution of hydrogen peroxide, over the course of 2.5 hours. Followingthe addition of the hydrogen peroxide, the reaction mixture ispostpolymerized at 85° C. for 1 hour and then cooled. A dispersion isobtained which has a solids content of 17.9% and an LD value of 94.

Dispersion 4

466.2 parts of water, 0.072 part of calcium acetate, 49.5 parts ofhydroxyethylstarch and 0.07 part of a-amylase are mixed in a reactionvessel fitted with reflux condenser and stirrer, and the mixture isheated to 85° C. with stirring. As soon as this temperature has beenreached, 0.041 part of α-amylase is added and the reaction mixture isstirred for 20 minutes. Then, in order to inactivate the enzyme, amixture of 8.22 parts of glacial acetic acid and 10.96 parts of a 1%strength aqueous iron(II) sulfate solution is added. 1.14 parts of a 30%strength aqueous solution of hydrogen peroxide are then added and, after20 minutes, 27.4 parts of 50% strength aqueous solution ofmethacrylamidopropyltrimethylammonium chloride, 4.1 parts of acrylicacid and 0.91 part of 30% strength hydrogen peroxide. At this point,feeding in of a mixture of 41.1 parts of styrene and 41.1 parts ofn-butyl acrylate, and feeding in of 58.4 parts of a 2.1% strengthhydrogen peroxide solution, are begun immediately. The monomer feedlasts for 2 hours and that of the hydrogen peroxide 2.25 hours.Following addition of the initiator, the reaction mixture ispostpolymerized for 1 hour at 85° C. and then cooled. An aqueousdispersion is obtained which has a solids content of 20.2% and an LDvalue of 98.

Dispersion 5

222.6 parts of water, 0.072 part of calcium acetate, 49.5 parts ofhydroxyethylstarch and 0.68 part of a 1% strength aqueous solution ofα-amylase are mixed and this reaction mixture is heated with stirring to85° C. The hydroxyethyl starch is first of all enzymatically degraded byadding 4.11 parts of a 1% strength aqueous solution of α-amylase overthe course of 20 minutes at 85° C. A mixture of 8.22 parts of glacialacetic acid and 11 parts of a 1% strength aqueous solution of iron(II)sulfate in water is then added. Subsequently, 1.14 part of 30% strengthhydrogen peroxide is metered in and oxidative degradation is carried outover the course of 20 minutes. Thereafter, 28.4 parts of a 50% strengthaqueous solution of methacrylamidopropyltrimethylammonium chloride, 4.1parts of acrylic acid and 0.91 part of 30% strength hydrogen peroxideare added. Directly following this, a monomer mixture of 41.1 parts ofstyrene and 41.1 parts of n-butyl acrylate and, separately, theinitiator feed of 61 parts of a 2.1% strength hydrogen peroxide solutionare added. The addition of the monomer feed is over after 2 hours andthat of the hydrogen peroxide after 2.25 hours. Following the end of theaddition of initiator, the reaction mixture is postpolymerized for 1hour. 4.4 parts of a 10% strength aqueous solution of the additionproduct of sodium bisulfite with formaldehyde are then added over thecourse of 40 minutes. After cooling, an aqueous dispersion is obtainedwhich has a solids content of 31% and an LD value of 94.

Dispersion 6

As described above, 461 parts of water, 0.07 part of calcium acetate,51.6 parts of hydroxypropylstarch and 0.72 part of a 1% strength aqueousα-amylase solution are mixed in a reaction vessel and heated withstirring to 85° C. At this temperature, enzymatic degradation is firstof all carried out over the course of 20 minutes by adding 4.29 parts of1% strength aqueous α-amylase solution and then oxidative degradation iscarried out over the course of 20 minutes by adding 8.57 parts ofglacial acetic acid, 11.4 parts of a 1% strength aqueous iron(II)sulfate solution and 1.19 parts of 30% strength hydrogen peroxide. 0.95part of 30% strength hydrogen peroxide and 14.3 parts of a 50% strengthaqueous solution of methacrylamidopropyltrimethylammonium chloride arethen added in one go and the metered addition of a mixture of 42.9 partsof styrene, 42.9 parts of n-butyl acrylate and 14.3 parts of a 50%strength aqueous solution of methacrylamidopropyltrimethylammoniumchloride and, separately, the metered addition of 61 parts of a 2.1%strength hydrogen peroxide solution are commenced immediately. Themonomers are metered in over the course of 2 hours and the initiatorover the course of 2.25 hours. Thereafter, the reaction mixture ispostpolymerized for 1 hour and then cooled. An aqueous dispersion isobtained which has a solids content of 20.4% and an LD value of 97.

Dispersion 7

As described above, 469.8 parts of water, 0.072 part of calcium acetate,43 parts of hydroxypropylstarch and 7.4 parts of hydroxyethylcelluloseare mixed and the mixture is heated with stirring to a temperature of85° C. 0.05 part of α-amylase is added and, after 20 minutes, a mixtureof 8.6 parts of glacial acetic acid and 11.4 parts of a 1% strengthaqueous iron(II) sulfate solution is also added. Following the additionof 2.3 parts of 30% strength hydrogen peroxide, the reaction mixture isheated to 95° C. Decomposition of the hydrogen peroxide is awaited, andthen the mixture is cooled to 85° C. and 37.4 parts of a 50% strengthaqueous solution of methacrylamidoethyltrimethylammoniummethosulfate and1.9 parts of 30% strength hydrogen peroxide are added in one go,followed immediately by the commencement of the metered addition, over 2hours, of a mixture of 40.7 parts of styrene and 40.7 parts of n-butylacrylate and, simultaneously but separately, over 2.25 hours, of 61parts of a 1.4% strength hydrogen peroxide solution. Following the endof the addition of initiator, the reaction mixture was postpolymerizedfor 1 hour. An aqueous dispersion is obtained which has a solids contentof 19.9%. The LD value is 95.

Dispersion 8

As described above, 457 parts of water, 0.06 part of calcium acetate, 43parts of hydroxypropylstarch, 7.44 parts of hydroxyethylcellulose and0.007 part of α-amylase are mixed and the mixture is heated withstirring to 85° C. As soon as this temperature has been reached, 4.3parts of a 1% strength aqueous solution of α-amylase are added.Thereafter, a mixture of 8.5 parts of glacial acetic acid and 11.4 partsof a 1% strength aqueous iron(II) sulfate solution is added again.Following the addition of 2.4 parts of a 30% strength hydrogen peroxidesolution, the reaction mixture is heated at 95° C. until the hydrogenperoxide has decomposed. The temperature is then lowered to 85° C., and28.6 parts of a 50% strength aqueous solution ofacrylamidoethyltrimethylammonium chloride and 0.97 part of a 39%strength aqueous solution of hydrogen peroxide are added to the mixturein one go. Directly following this, the addition is made of a mixture of47.1 parts of acrylonitrile and 38.6 parts of n-butyl acrylate over thecourse of 2.25 hours and, simultaneously but separately from the monomerfeed, of 61 parts of a 2.11% strength solution of hydrogen peroxide.After the customary postpolymerization and cooling, an aqueousdispersion is obtained which has a solids content of 20% and an LD valueof 91.

Dispersion 9

469.8 parts of water, 0.072 part of calcium acetate, 43 parts ofhydroxypropylstarch and 7.4 parts of hydroxyethylcellulose are mixedunder nitrogen in a reaction vessel fitted with reflux condenser andstirrer, and the mixture is heated with stirring to a temperature of 85°C. Then 0.05 part of α-amylase is added. After 20 minutes, a mixture of8.6 parts of glacial acetic acid and 11.4 parts of a 1% strength aqueoussolution of iron(II) sulfate is added. Following the addition of 2.3parts by weight of 30% strength hydrogen peroxide, the contents of theflask are heated at 95° C. until the hydrogen peroxide is decomposed.Thereafter, the temperature is lowered to 85° C. Following the additionof 31.7 parts of a 45% strength aqueous solution of vinylimidazole whichis quaternized with dimethyl sulfate, and 0.95 part of 30% strengthhydrogen peroxide, the metered addition of a monomer mixture comprising42.9 parts of styrene and 42.9 parts of n-butyl acrylate is commencedimmediately, as is the metered addition of the initiator feed comprising61 parts of a 2.1% strength hydrogen peroxide solution. The feed timesare as in the preparation of dispersion 10. Subsequently, over thecourse of 40 minutes, 2.9 parts by weight of a 10% strength aqueoussolution of the adduct of sodium bisulfate and formaldehyde are added,and then the reaction mixture is cooled. An aqueous dispersion isobtained which has a solids content of 20.4% and an LD value of 94.

Dispersion 10

524.7 parts of water, 0.072 part of calcium acetate, 71.2 parts ofhydroxypropylstarch and 8.8 parts by weight of hydroxyethyl-celluloseare mixed under nitrogen in a polymerization apparatus fitted withreflux condenser and stirrer, and the mixture is heated with stirring to85° C. Then 0.06 part of α-amylase is added. After 20 minutes, a mixtureof 10.1 parts of glacial acetic acid and 13.5 parts of 1% strengthaqueous iron(II) sulfate solution are added. Following the addition of2.8 parts by weight of 30% strength hydrogen peroxide, the flask isheated at 95° C. until the hydrogen peroxide has decomposed. Thereafter,the temperature is lowered to 85° C. and 37.5 parts of a 45% strengthaqueous solution of vinylimidazole which is quaternized with dimethylsulfate, and 2.23 parts of 30% strength hydrogen peroxide are added tothe reaction mixture in one go. Immediately thereafter, the meteredaddition of the monomer mixture comprising 41.4 parts of styrene, 20.4parts of n-butyl acrylate, 20.4 parts of tert-butyl acrylate and 0.68part of acrylic acid together with 0.17 part of ethylhexyl thioglycolateis commenced. Simultaneously therewith, the feeding-in of 72 parts byweight of a 1.39% strength aqueous hydrogen peroxide solution isstarted. Feed times and postpolymerization are as described forDispersion 12. Subsequently, a further 0.57 part of a 30% strengthhydrogen peroxide solution is added, 10 minutes are allowed to elapse,and then the reaction mixture is cooled. An aqueous dispersion isobtained which has a solids content of 19.7% and an LD value of 97.

Dispersion 11

776 parts of water, 0.125 part of calcium acetate, 165 parts ofhydroxypropylstarch and 13 parts of hydroxypropylcellulose are mixedunder nitrogen in a polymerization apparatus fitted with refluxcondenser and stirrer, and the mixture is heated with stirring to 85° C.As soon as this temperature has been reached, 0.09 part of α-amylase isadded in one go. After 20 minutes, a mixture of 15 parts of glacialacetic acid and 20 parts of a 1% strength aqueous iron(II) sulfatesolution is added. Following the addition of 4.17 parts of 30% strengthhydrogen peroxide and of 5 parts of a 10% strength aqueous solution ofthe adduct of sodium bisulfite and formaldehyde, the reaction mixture isstirred for 20 minutes, and then 55.5 parts of a 45% strength aqueoussolution of vinylimidazole which is quaternized with dimethyl sulfate,and 1.67 parts of 30% strength hydrogen peroxide are added. Directlythereafter, a monomer mixture comprising 37.5 parts of styrene, 18.8parts of n-butyl acrylate and 18.7 parts of tert-butyl acrylate togetherwith 0.25 parts of ethylhexyl thioglycolate is metered in over thecourse of 2 hours, and, simultaneously but separately over the course of2.25 hours, the addition of 106 parts of a 1.4% strength hydrogenperoxide solution is commenced. After postpolymerization for one hour,0.38 part of a 30% strength hydrogen peroxide solution is added and thereaction mixture is stirred at 85° C. for 10 minutes and then allowed tocool. An aqueous dispersion is obtained which has a solids content of20.6% and an LD value of 98.

Dispersion 12

455.3 parts of water, 0.072 part of calcium acetate, 43 parts ofhydroxypropylstarch and 7.4 parts of hydroxyethylcellulose are mixedunder nitrogen in a polymerization vessel fitted with reflux condenserand stirrer, and the mixture is heated with stirring to 85° C. At thistemperature, 0.045 part of α-amylase and, after 20 minutes, a mixture of8.6 parts of glacial acetic acid and 11.4 parts of a 1% strength aqueousiron(II) sulfate solution are added. Following the addition of 2.4 partsof a 30% strength hydrogen peroxide solution, the contents of the flaskare heated at 95° C. until the hydrogen peroxide has decomposed.Thereafter, the temperature is lowered to 85° C. again. Following theaddition of 31.7 parts of a 45% strength aqueous solution ofvinylimidazole which is quaternized with dimethyl sulfate, and 0.95parts of a 30% strength aqueous hydrogen peroxide solution, a monomermixture comprising 42.9 parts of styrene, 21.43 parts of n-butylacrylate and 21.43 parts of tert-butyl acrylate together with 0.143 partof tert-dodecylmercaptan is added over the course of 2 hours and,simultaneously but separately, a feed comprising 61 parts of a 1.2%strength hydrogen peroxide solution is added over the course of 2.25hours. Following the customary postpolymerization and cooling, anaqueous dispersion is obtained which has a solids content of 19.9% andan LD value of 92.

Dispersion 13

456 parts of water, 0.07 part of calcium acetate, 38.7 parts ofhydroxypropylstarch and 11.2 parts of hydroxyethylcellulose togetherwith 0.005 part of α-amylase are mixed under nitrogen in apolymerization vessel fitted with stirrer and reflux condenser, and themixture is heated with stirring to 85° C. As soon as this temperaturehas been reached, 0.045 part of α-amylase is added, the mixture isstirred, and after exactly 20 minutes a mixture of 8.5 parts of glacialacetic acid and 11.4 parts of a 1% strength aqueous iron(II) sulfatesolution is added. Following the addition of 2.4 parts of 30% strengthhydrogen peroxide, the decomposition of the hydrogen peroxide isawaited. Then 31.75 parts of a 45% strength aqueous solution ofvinylimidazole which is quaternized with dimethyl sulfate, and 0.95 partof a 30% strength hydrogen peroxide solution are added. Directlythereafter, the metered addition of a monomer mixture comprising 42.9parts of styrene, 21.4 parts of n-butyl acrylate and 21.4 parts oftert-butyl acrylate is commenced. Simultaneously with the addition ofthe monomers, 61 parts of a 2.11% strength hydrogen peroxide solutionare metered in. The monomers are metered in over the course of 2 hoursand the initiator over the course of 2.5 hours. Followingpostpolymerization and cooling, an aqueous dispersion is obtained whichhas a solids content of 19.7% and an LD value of 90.

Dispersion 14

31.5 parts of glacial acetic acid are initially introduced undernitrogen into a polymerization apparatus fitted with stirrer and refluxcondenser, and, with stirring and in succession, 38.3 parts of styrene,12.6 parts of dimethylaminopropylmethacrylamide and 5.5 parts of acrylicacid are added. Following the addition of 1.5 parts ofazodiisobutyronitrile, the reaction mixture is heated to a temperatureof 85° C. 15 minutes after reaching 85° C., 1.5 parts ofazodiisobutyronitrile are added and, after a further 15 minutes, afurther 1.5 parts of azodiisobutyronitrile. After a further 30 minutes,the viscous solution is diluted with 334 parts of water containing 0.047part of iron(II) sulfate and the reaction mixture is heated to 85° C. Atthis temperature, a monomer mixture comprising 50 parts of styrene, 25parts of n-butyl acrylate and 25 parts of tert-butyl acrylate is meteredin over the course of 2 hours and, simultaneously but separately, theinitiator feed comprising 27 parts of a 2.5% strength solution ofhydrogen peroxide is metered in over the course of 2.25 hours. Thereaction mixture is then postpolymerized for 1 hour and, subsequently,cooled. An aqueous dispersion is obtained which has a solids content of28.8% and an LD value of 99.

Dispersion 15

28.6 parts of glacial acetic acid are introduced under nitrogen into apolymerization apparatus fitted with a stirrer and a reflux condenser,and, with stirring and in succession, 29.3 parts of styrene, 9.57 partsof dimethylaminopropylmethacrylamide and 4 parts of acrylic acid areadded. Following the addition of 1.5 parts of azodiisobutyronitrile, thereaction mixture is heated to 85° C. After 15 minutes, a further 1.5parts of azodiisobutyronitrile are added, and after a further 15 minutesa further 1.5 parts of azodiisobutyronitrile. 30 minutes after thestart, the viscous solution is diluted with 302 parts of watercontaining 0.043 part of iron(II) sulfate. The reaction mixture is thenheated to 85° C. As soon as this temperature has been reached, a monomermixture comprising 50 parts of styrene, 25 parts of n-butyl acrylate and25 parts of tert-butyl acrylate is metered in over the course of 2hours. 4.2 parts of a 5% strength hydrogen peroxide solution are added,and, simultaneously with the monomer feed over the course of 2.25 hours,27 parts of a 5% strength hydrogen peroxide solution are also added.Following postpolymerization for 1 hour and subsequent cooling, adispersion is obtained which has a solids content of 29% and an LD valueof 98.

Dispersion 16

31.5 parts of glacial acetic acid are initially introduced undernitrogen into a polymerization apparatus fitted with a stirrer and areflux condenser, and, with stirring and in succession, 39.4 parts ofstyrene, 12.6 parts of dimethylaminopropylmethacrylamide and 5.51 partsof acrylic acid are added. Following the addition of 1.5 parts ofazodiisobutyronitrile, the mixture is heated to 85° C. 15 minutes afterthe start of the polymerization, a further 1.5 parts of azobutyronitrileare added and, after a further 15 minutes, a further 1.5 parts--the samequantity--of the initiator. After 30 minutes the viscous solution isdiluted with 334 parts of water containing 0.047 part of iron(II)sulfate, accompanied by slow stirring and heating to 85° C. As soon asthe temperature of 85° C. has been reached, a monomer mixture comprising50.1 parts of styrene, 25 parts of n-butyl acrylate and 25 parts ofmethyl acrylate is metered in over the course of 2 hours. 4.5 parts byweight of a 5% strength hydrogen peroxide solution are added in one go,and 23.6 parts of a 5% strength hydrogen peroxide solution are meteredin over the course of 2.25 hours. 1 hour after the end of the additionof hydrogen peroxide, the reaction mixture is postpolymerized at 85° C.and then cooled. An aqueous dispersion is obtained which has a solidscontent of 28.8% and an LD value of 97.

Dispersion 17 (comparison)

410 parts of water, 0.07 part of calcium acetate, 17.2 parts of acationic potato starch, 14.9 parts of hydroxyethylcellulose and 14.3parts of gelatin are mixed under nitrogen in a polymerization apparatusfitted with a stirrer and reflux condenser, and the mixture is heatedwith stirring to 85° C. Then, at this temperature, 8.6 parts of glacialacetic acid and a solution of 0.057 part of iron(II) sulfate in 5.65parts of water are added. Following the metered addition of 4.76 partsof a 30% strength hydrogen peroxide solution, the decomposition of thehydrogen peroxide is awaited. Then 0.71 part of 30% strength hydrogenperoxide is added and, directly thereafter, the feeding-in of a monomermixture comprising 22.7 parts of styrene, 47.3 parts of n-butyl acrylateand 30 parts of methyl acrylate is begun and, simultaneously butseparately, the metered addition of 61 parts of a 1.64% strengthhydrogen peroxide solution is commenced. The monomers are metered inover the course of 2 hours and the hydrogen peroxide over the course of2.5 hours. After a postpolymerization time of 1 hour at 85° C., thereaction mixture is cooled. An aqueous dispersion is obtained which hasa solids content of 19% and an LD value of 98.

Dispersion 18 (comparison)

In a reaction vessel fitted with reflux condenser and stirrer, 42.5parts of water, 0.05 part of calcium acetate and 24.7 parts of thecationic potato starch together with 0.006 part of α-amylase are heatedwith stirring to 85° C. Then 0.036 part of α-amylase is added. After 20minutes, a mixture of 5 parts of glacial acetic acid and 4.8 parts of a1% strength solution of FeSO.sub..4 7H₂ O in water is added. Thereafter,6 parts of 5% strength hydrogen peroxide are added. After 20 minutes, afurther 3.6 parts of 5% strength hydrogen peroxide are added and thefeeding in of a mixture of 55 parts of acrylonitrile and 45 parts ofn-butyl acrylate, and of 31.3 parts of a 5% strength hydrogen peroxidesolution in water, is commenced immediately. The monomer feed is meteredin over the course of 2.5 hours and that of the hydrogen peroxide over 3hours. After the end of the feeds, postpolymerization is carried out for1 hour and the mixture is then cooled. The dispersion has a solidscontent of 35.2% and an LD value of 85.

The dispersions described above were used as coating compositions forsized papers and then the suitability of the resulting papers for inkjetprinting was assessed. For these tests, 2 papers were used:

Paper 1

This paper was prepared by dewatering a stock comprising 50% bleachedpine sulfite pulp, 50% bleached hardwood sulfite pulp and 30% chalk,based on dry pulp. The paper was engine-sized to a Cobb value(determined in accordance with DIN 53132) of 54 g/m² and had a weightper unit area of 70 g/m². The freeness was 25° SR (Schopper-Riegler) andthe ash content was 15%.

Paper 2

This test paper was obtained by dewatering a paper stock which contained10% bleached pinewood sulfite pulp, 90% bleached hardwood sulfate pulpand 40% chalk, based on dry pulp. The paper was engine-sized to a Cobbvalue of 20 g/m² and had a weight per unit area of 80 g/m². The freenesswas 25° SR and the ash content was 25%.

To test the dispersions described above, preparation solutions wereprepared which contained, respectively, 2.5, 5, 10 and 20 g/l ofcopolymer of the particular dispersion to be tested (based on the solidscontent of the dispersions) and 60 g/l of an oxidatively degraded starchwith an intrinsic viscosity of 0.36 dl/g. The liquor uptake in the caseof paper 1 was about 80% and in the case of paper 2 was about 20%.

The inkjet printability properties were determined on the basis of inkdensity, strikethrough and showthrough on the reverse side and the waterfastness of the inkjet-printed image in accordance with the methodsindicated above. The results obtained with paper 1 are shown in Table 1below, and those obtained with paper 2 are listed in Table 2.

                                      TABLE 1                                     __________________________________________________________________________                       Paper 1   Paper 1                                                   Paper 1   Ink density after                                                                       Ink density of the                                        Ink density of the                                                                      storage in water at                                                                     reverse side at                                           front side at                                                                           5 g/l                                                                            10 g/l                                                                            20 g/l                                                                           5 g/l                                                                            10 g/l                                                                            20 g/l                                    Dispersion                                                                             5 g/l                                                                            10 g/l                                                                            20 g/l                                                                           in the preparation                                                                      in the preparation                               No.      copolymer solution  solution                                         __________________________________________________________________________    Ex.                                                                           No.                                                                           1   1    1.33                                                                             1.55                                                                              1.71                                                                             1.27                                                                             1.39                                                                              1.55                                                                             0.25                                                                             0.1 0.09                                      2   2    1.33                                                                             1.61                                                                              1.76                                                                             1.18                                                                             1.49                                                                              1.59                                                                             0.18                                                                             0.09                                                                              0.08                                      3   3    1.48                                                                             1.83                                                                              1.88                                                                             1.51                                                                             1.68                                                                              1.59                                                                             0.14                                                                             0.08                                                                              0.08                                      4   4    1.53                                                                             1.75                                                                              1.77                                                                             1.08                                                                             1.56                                                                              1.62                                                                             0.11                                                                             0.08                                                                              0.08                                      5   5    1.47                                                                             1.78                                                                              1.81                                                                             1.26                                                                             1.61                                                                              1.64                                                                             0.11                                                                             0.11                                                                              0.09                                      6   6    1.55                                                                             1.76                                                                              1.78                                                                             1.26                                                                             1.56                                                                              1.64                                                                             0.12                                                                             0.08                                                                              0.1                                       7   7    1.59                                                                             1.75                                                                              1.73                                                                             1.44                                                                             1.57                                                                              1.58                                                                             0.17                                                                             0.1 0.09                                      8   8    1.76                                                                             1.72                                                                              1.73                                                                             1.54                                                                             1.57                                                                              1.53                                                                             0.09                                                                             0.08                                                                              0.07                                      9   9    1.62                                                                             1.86                                                                              1.84                                                                             1.61                                                                             1.71                                                                              1.77                                                                             0.1                                                                              0.15                                                                              0.07                                      10  10   1.81                                                                             1.72                                                                              1.89                                                                             1.57                                                                             1.61                                                                              1.68                                                                             0.1                                                                              0.09                                                                              0.09                                      11  11   1.55                                                                             1.88                                                                              1.89                                                                             1.47                                                                             1.62                                                                              1.66                                                                             0.1                                                                              0.08                                                                              0.08                                      12  12   1.85                                                                             1.92                                                                              -- 1.61                                                                             1.7 -- -- --  --                                        13  13   1.79                                                                             1.81                                                                              -- 1.59                                                                             1.64                                                                              -- -- --  --                                        14  14   1.80                                                                             1.84                                                                              -- 1.65                                                                             1.69                                                                              -- -- --  --                                        15  15   1.89                                                                             1.88                                                                              -- 1.66                                                                             1.67                                                                              -- -- --  --                                        16  16   1.82                                                                             1.87                                                                              -- 1.62                                                                             1.66                                                                              -- -- --  --                                        Comp.                                                                         Ex.                                                                           1   17   -- --  1.85                                                                             -- --  1.23                                                                             -- --  0.07                                      2   18   1.80                                                                             1.80                                                                              1.77                                                                             1.43                                                                             1.40                                                                              1.37                                                                             0.06                                                                             0.05                                                                              0.05                                      __________________________________________________________________________

                                      TABLE 2                                     __________________________________________________________________________                       Paper 2   Paper 2                                                   Paper 2   Ink density after                                                                       Ink density of the                                        Ink density of the                                                                      storage in water at                                                                     reverse side at                                           front side at                                                                           5 g/l                                                                            10 g/l                                                                            20 g/l                                                                           5 g/l                                                                            10 g/l                                                                            20 g/l                                    Ex. Dispersion                                                                         5 g/l                                                                            10 g/l                                                                            20 g/l                                                                           in the preparation                                                                      in the preparation                               No. No.  copolymer solution  solution                                         __________________________________________________________________________    17  12   1.79                                                                             1.84                                                                              1.88                                                                             1.56                                                                             1.76                                                                              1.78                                                                             0.07                                                                             0.07                                                                              0.07                                      18  13   1.7                                                                              1.75                                                                              1.76                                                                             1.47                                                                             1.48                                                                              1.55                                                                             0.07                                                                             0.02                                                                              0.02                                      __________________________________________________________________________

We claim:
 1. A process for the preparation of a recording materialcomprising applying an aqueous coating composition to one or both sidesof a sheet of paper for an inkjet printer wherein said coatingcomposition is an aqueous dispersion consisting essentially from 20 to200 g/l of starch and from 0.5 to 50 g/l of a copolymer formed byemulsion copolymerization of 100 parts by weight of a monomer mixtureconsisting essentially of(a) from 10 to 65 parts by weight of a monomerselected from the group consisting of styrene, α-methylstyrene,acrylonitrile, methacrylonitrile, and mixtures thereof, (b) from 30 to85 parts by weight of a monomer selected from the group consisting ofacrylic ester with a C₁ -C₁₈ alcohol, methacrylic ester with a C₁ -C₁₈alcohol and mixtures thereof, (c) from 5 to 25 parts by weight of amonomer containing a tertiary, quaternary amino group, or a mixturethereof, and (d) from 0 to 20 parts by weight of anothermonoethylenically unsaturated monomer in an aqueous medium in thepresence of from 12 to 300% by weight, based on said monomer mixture, ofat least one natural or synthetic protective colloid.
 2. The process asclaimed in claim 1, wherein the synthetic protective colloids employedare polyvinyl alcohol, polyvinylpyrrolidone and/or water-solublecationic copolymers which contain tertiary and/or quaternary aminogroups.
 3. The process of claim 1, wherein said synthetic protectivecolloid is prepared by solution polymerization of a monomer mixturecomprising(1) from 40 to 80% by weight of a monomer selected from thegroup consisting of styrene, acrylonitrile, methacrylonitrile, acrylicor methacrylic ester of C₄ -C₁₈ alcohols and mixtures thereof, (2) from15 to 50% by weight of a monomer containing a tertiary, quaternary aminogroup, or a mixture thereof and (3) from 5 to 25% by weight of a monomerselected from the group consisting of acrylic acid, methacrylic acid,acrylamide, methacrylamide and mixtures thereof in a solvent selectedfrom the group consisting of a saturated C₁ -C₅ -carboxylic acid, anester of said carboxylic acid with a saturated C₁ -C₆ alcohol, asaturated C₁ -C₆ alcohol, a saturated ketone and mixtures thereof. 4.The process as claimed in claim 1, wherein natural protective colloidsemployed are hydroxyethylcellulose, hydroxyethyl-starch and/orhydroxypropylstarch.
 5. The process of claim 1, wherein the protectivecolloid is used in quantities of from 25 to 160% by weight, based on thetotal monomer mixture.
 6. A process for the preparation of a recordingmaterial comprising applying an aqueous coating composition to one orboth sides of a sheet of paper for an inkjet printer wherein saidcoating composition is an aqueous dispersion consisting essentially from20 g/l to 200 g/l of starch and from 0.5 to 50 g/l of a copolymer formedby emulsion copolymerization of 100 parts by weight of a monomer mixtureconsisting essentially of(a) from 10 to 65 parts by weight of a monomerselected from the group consisting of styrene, α-methylstyrene,acrylonitrile, methacrylonitrile, and mixture thereof, (b) from 30 to 85parts by weight of a monomer selected from the group consisting ofacrylic ester with a C₁ -C₁₈ alcohol, methacrylic ester with a C₁ -C₁₈alcohol and mixtures thereof, (c) from 0 to 25 parts by weight of amonomer containing tertiary amino group, a monomer containing aquaternary amino group, or a mixture thereof, and (d) from 0 to 20 partsby weight of another monoethylenically unsaturated monomer in an aqueousmedium in the presence of from 12 to 300% by weight, based on totalmonomer mixture, of a synthetic cationic protective colloid.